Some of the members have past experience in such bipartisan groups. As many as nine senators, including a member of the Democratic leadership, are working on a new resolution that would ultimately authorize the use of force against Syria unless the country's chemical weapons stockpiles can be secured by the international community.

Under the proposal, which is still in the conceptual stages, the United Nations would need to agree to a resolution acknowledging that the Syrian government was responsible for gassing its own people. Then, the United Nations would need to act to secure Syria's remaining weapons to prevent future use, according to a source familiar with the discussions. Otherwise, the measure would authorize the use of force.

The source indicated that Democratic Sens. Bob Casey of Pennsylvania, Chris Coons of Delaware, Carl Levin of Michigan and Charles E. Schumer of New York were said to be working with four Republican senators on the plan.

The Republicans involved include a familiar trio: Kelly Ayotte of New Hampshire, Lindsey Graham of South Carolina and John McCain of Arizona. They're joined in the effort by Intelligence Vice Chairman Saxby Chambliss of Georgia.

Foreign Relations Chairman Robert Menendez, D-N.J., was also said by the source to be involved in the conversations on the new resolution. Menendez was the lead author of the use-of-force resolution reported out by his committee that is lined up for Senate floor consideration.

Following initial reports of a Russian proposal to have the international community take custody of Syria's chemical weapons, Graham and McCain said in a joint statement Monday that the Obama administration should act quickly to take the proposal to the United Nations.

"The only credible way for the Obama Administration to test this proposal is to immediately introduce a U.N. Security Council Resolution that spells out in clear, detailed terms exactly what the international community should expect of the Assad regime if it is serious about abandoning its weapons of mass destruction — weapons that it does not even admit to possessing at this point," Graham and McCain said. "Such a resolution must include specific requirements for immediate and intrusive inspections, unfettered international access to every site and suspected site in Syria possessing any weapons of mass destruction, guarantees for secure freedom of movement for all international inspectors, immediate steps by Assad to begin transferring his weapons of mass destruction to international custody, and clear consequences and triggers for action if obligations are not met by a time certain, among other commitments."